Watch my video review of Citizenfour, the chilling documentary by Laura Poitras about Edward Snowden, the former NSA contractor who leaked tens of thousands of pages of classified documents about vast U.S. spying operations at home and abroad. The impact of those leaks continues to reverberate around the world.

Poitras, a filmmaker and journalist, previously was nominated for an Oscar for her film My Country, My Country. Here, she records the process that led to revelations she and colleague Glenn Greenwald published in the Guardian after Snowden anonymously contacted her under the online pseudonym of citizenfour. The resulting leaks helped Poitras win several awards for investigative journalism, while Snowden fled to Russia, where he remains in hiding.